Subject: [Sip] Doubts about Handling of RR in GRUU

From: "George Foti (QA/EMC)" <[email-masked]>
Date: Tue, 22 Nov 2005 07:41:02 -0600

Hi,

I have a question on the GRUU draft when it comes to Record Routing. 

I am not sure if the desired result, as depicted in the draft can be achieved with the current description.

The draft talks about the edge proxy removing itself from the RR of responses both at the originating domain and terminating domain with the desired result being as quoted from the spec:

"
Removing its Record-Route value from the response will result in the
   route set being seen differently by the caller and callee; the callee
   (which is the user agent in the figure) will have a route set entry
   for its edge proxy, while the caller will not.  The caller will have
   a route set entry for its edge proxy, while the callee will not."

Lets take an example to see where the problem is as far as the 

description in the draft is concerned So lets take the following case:

 UE1--- HP1------EP1..........................HP2------EP2---------UE2

 Both UE1, and UE2 acquired GRUUs, and both EP1 & EP2 are in the path 

 for their subsequent UEs when they REGISTER.

If UE1 initiates an INVITE and all proxies insert themselves in 

the RR, so we have the RR arriving at UE2 having EP2, HP1, EP1, HP1.

Then according to the draft both EP2, and EP1 should remove themselves

from the response to the INVITE.

So, if UE2 returns a 200 OK with the RR, EP2 removes itself, and EP1 removes itself as well.

So UE1 sees a RR including HP1,HP2, and that the route set it has

While UE2 have a route set entry that includes all 4 proxies, EP2, HP1, EP1, HP1.

Am I misinterpreting the spec?

Rgds/gf

Ericsson Canada

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---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 22 Nov 2005 12:49:02 -0500

George,

I just recently noticed this as well. I don't think you are 
misinterpretting the draft, I think the draft is in error.

The problem is that on the terminating side, to get the intended result, 
EP2 needs to leave itself out of the R-R in the request, but add itself 
in to the R-R in the response. For that to work when there are more 
complex topologies beyond it, when it forwards the request it needs to 
remember where the top of the R-R stack is, so that it will know *where* 
in the R-R to place itself when the response arrives.

	Paul

George Foti (QA/EMC) wrote:
> The draft talks about the edge proxy removing itself from the RR of 
> responses both at the originating domain and terminating domain with the 
> desired result being as quoted from the spec:
> 
>  
> 
> "
> 
> ------------------------------------------------------------------------
>